RF induction and analog junction techniques for finding opens

Abstract

In response to the need for fast and simple methods for detecting and diagnosing open pins on SMT devices, board test manufactures have introduced power-off, vectorless test techniques that provide reasonable fault coverage with little programming effort. This paper describes two techniques: the RF induction and the analog junction technique. The RF technique applies a 200-500kHz signal to a spiral loop antenna located over the device. This antenna or "inducer" produces an AC signals at the device pin under test which the in-circuit tester measures. The technique requires one inducer for each device to be tested. The test system software automatically learns the characteristics of the device being tested. The users need only describe the connections between the device and the tester, identify the device's power and ground pins, and which inducer is mounted over the part. The analog junction technique uses the device protection diodes. It requires no fixture hardware, relying only on the bed-of-nails contact with the device pins. The analog junction technique applies voltage to one pin of the device, causing current to flow between the pin and the device ground lead. Voltage is then applied another pin on the device, causing current to flow between this pin and the ground lead. Both the analog junction and RF induction techniques are effective means for detecting opens on digital devices.